The present invention relates to an interbay transportation system for transporting a semi-processed product from a previous process step to the next process step (i.e. from one bay to another bay) in a manufacturing plant. More particularly, the present invention relates to an interbay transportation system that includes stockers (or storage shelves) for individual process steps to allow process-waiting and transportation-waiting, and transport pods (or cassettes) containing semi-processed products conveyed from the stocker for a previous process step and to the stocker for the next process step.
A semiconductor product, such as a semiconductor memory or a microprocessor, is produced in a procedure in which many elements such as transistors and capacitors as well as wirings connecting the elements are finely and precisely formed on a semiconductor wafer having a diameter of 200 to 300 mm, the wafer is cut into individual products, and the individual cut-out products are encapsulated by resin. Thus, formation of the elements and wirings on the semiconductor wafer is significantly important for manufacturing semiconductor products, and is carried out through various and many process steps.
In each of the aforementioned process steps, a dedicated manufacturing apparatus (hereinafter referred to as process equipment) is used. As such, an interbay transportation system is necessary to transport a semiconductor wafer completed in processing by the process equipment in a previous step to the process equipment in the next process step.
Hereinafter, an example of such interbay transportation system will be described with reference to FIG. 1.
Generally, in a semiconductor-product manufacturing plant, a plurality of rooms (each of which will be referred to as a bay) are provided in a clean room, and a plurality of process equipment are provided in each of the bays. In the example shown in FIG. 1, six bays (bay 1 to bay 6) are provided in a clean room, and three or four pieces of equipment are provided in each of the bays (for example, process equipment 11, 12 and 13 for the bay 1).
An OHS (Over Head Shuttle) 8 is provided to perform transportation between bays, that is, interbay transportation. The OHS 8 is configured to include a guide rail circularly visiting the individual bays, and OHS vehicles 80 travelling along the guide rail. A plurality of semiconductor wafers (for example, 25 pieces) are housed in one pod, loaded onto the OHS vehicle 80, and carried from one bay to another. Ordinarily, a plurality of the pods (for example, 2 pods) can be loaded onto the OHS vehicle 80.
A storage shelf (which will be referred to as a stocker) is provided for each of the bays to receive from the OHS vehicle the pod (semiconductor wafers) that is to be processed in the bay, and to hand a process-completed pod to the OHS vehicles. In the example shown in FIG. 1, stockers 10 to 60 are provided for the respective bays 1 to 6.
Hereinafter, a practical interbay transportation will be described using FIG. 2.
A pod (semiconductor wafers) to be processed by process equipment 11 is loaded onto an OHS vehicle 80 and transported to a bay 1. Then, the pod is stored in a stocker 10 for the bay 1 (see an arrow 101 in FIG. 2). An intrabay transportation system, which is provided in the bay 1, takes out the pod from the stocker 10, and then feeds it into the process equipment 11 (see an arrow 102 in FIG. 2). Upon completion of processing in the process equipment 11, the intrabay transportation system returns the process-completed pod to the stocker 10 (see an arrow 103 in FIG. 2).
Subsequently, the process-completed pod is transported to the next process step. Description is made hereinbelow assuming that process equipment 53 executes the next process step. An OHS 8 transports the process-completed pod to a bay 5, and the pod is stored into a stocker 50 (see an arrow 104 in FIG. 2). An intrabay transportation system in the bay 5 takes out the pod from the stocker 50, and then feeds it into the process equipment 53 (see an arrow 105 in FIG. 2). Upon completion of processing in the process equipment 53, the intrabay transportation system returns the process-completed pod to the stocker 50 (see an arrow 106 in FIG. 2).
The OHS 8 takes out the process-completed pod from the stocker 50, and then transports the pod to a stocker 20 for the next process step (see an arrow 107 in FIG. 2). Thereafter, in the same manner, transportation of a pod (semiconductor wafers) and processing in the process equipment are iterated, thereby allowing the manufacture of semiconductor products to proceed.
In the interbay transportation system described above, a request is issued to cause the pod to be transported to the next process step (for example, the stocker 50) when the process-completed pod in the previous process equipment is returned to a stocker (for example, the stocker 10). In response, the OHS vehicle travels to the stocker 10, receives the pod, and then transports the pod to the stocker 50.
At this time, the stocker 50 may be full for some reasons. That is, pods to be processed by process equipment in the bay 5 are increased, or process equipment(s) in the bay 5 has malfunctioned. In such a case, when a free space for one pod occurs, transportation from the stocker 10 to the stocker 50 is immediately started. Therefore, non-urgent transportation takes place and hinders high-urgency transportation. Furthermore, the full loading capacity of the OHS vehicle cannot be used up, so that the transportation efficiency is reduced.
In addition, as has already been described, although the OHS vehicle has the capacity of transporting the plurality of pods, a transportation request is issued in units of one pod. Therefore, unless processing for the second pod is timely completed, the OHS vehicle transports only a single pod, and thereby, the transportation efficiency is also reduced. If the transportation request is issued after completion of processing of the second pod to avoid the problem, a wait time can occur in process equipment of the next step because the pod is not timely transported thereto, thereby reducing the operation rate of the process equipment.
In order to solve the above-described problems, an interbay transportation system of the present invention includs bays in which process equipment are provided, stockers provided for the individual bays, and a vehicle traveling through the stockers for transporting a semi-processed product from one of the stockers to another, and is characterized in that timing to start transportation is determined according to the operation status of the process equipment and the number of semi-processed products in the stocker.
Moreover, an interbay transportation system according to the present invention includes bays in which process equipment are provided, stockers provided for the individual bays, and a vehicle traveling through the stockers for transporting a semi-processed product from one of the stockers to another, and furthermore, a buffer stocker in which a semi-processed product is temporary shelved.
Further, a method of interbay transportation according to the present invention is associated with an interbay transportation system including bays in which process equipment are provided, stockers provided for the individual bays, and a vehicle capable of loading a plurality of semi-processed products. Semi-processed products are transported from a stocker of a bay including process equipment for a previous process step to a stocker for a bay including process equipment for the next process step by the vehicle. In the method of the present invention, a comparison is performed between a time by completion of processing in the process equipment in the next process step and a time of transportation between the stockers. Following the result of the comparison, transportation by the vehicle is awaited until the time by completion of processing becomes equal to the time of transportation between the stockers. During a period of the awaiting, another semi-processed product that was completed in processing in the previous process step may be returned to the stocker for the previous process step. Therefore, by transporting the pod which is returned to the stocker during a period of the awaiting together with the first pod, the efficiency in transportation is improved.
A method of interbay transportation according to the present invention is associated with an interbay transportation system including bays in which process equipment are provided, stockers provided for the individual bays, and a vehicle capable of loading a plurality of semi-processed products. Semi-processed products are transported from a stocker of a bay including process equipment for a previous process step to a stocker of a bay including process equipment for the next process step by the vehicle. In the method of the present invention, the status of the process equipment for the next process step is detected. In case where the process equipment for the next process step is not operating, a semi-processed product completed in processing in the previous process step is transported only one time from the stocker for the previous process step to the stocker for the next process step. A semi-processed product to follow is kept to stay in the stocker for the previous process step. Therefor, the problem in which the stocker for the next process step is jammed up with the process-waiting pods does not arise.
A method of interbay transportation according to the present invention is associated with an interbay transportation system including bays in which process equipment are provided, stockers provided for the individual bays, a buffer stocker in which a semi-processed product is temporary shelved, and a vehicle capable of loading a plurality of semi-processed products. Semi-processed products are transported from a stocker of a bay including process equipment for a previous process step to a stocker for a bay including process equipment for the next process step by the vehicle. In the method of the present invention, the status of the process equipment for the next step and/or the status of the stocker for the next step are detected. In the case where the process equipment for the next process step is not operating or in the case where the stocker for the next process step is full, a semi-processed product to be transported to the stocker for the next process step is temporarily shelved in the buffer stocker. Therefor, the problem in which the stocker for the previous process step is jammed up with the transportation-waiting pods does not arise.
A method of interbay transportation according to the present invention is associated with an interbay transportation system including bays in which process equipment are provided, stockers provided for the individual bays, a buffer stocker in which a semi-processed product is temporary shelved, and a vehicle capable of loading a plurality of semi-processed products. Semi-processed product are transported from a stocker of a bay including process equipment for a previous process step to a stocker for a bay including process equipment for the next process step by the vehicle. In the method of the present invention, the number of semi-processed products in the stocker for the next process step is detected. In the case where the number of semi-processed products in the stocker for the next process step is equal to or larger than a prescribed number, a time until the number of semi-processed product in the stocker for the next process step becomes smaller than the prescribed number is determined. Moreover, a difference in required time between detour transportation via the buffer stocker and direct transportation without the buffer stocker is also determined. When the time until the number of semi-processed products becomes smaller than the predetermined number is longer than the time difference between detour and direct transportation, a semi-processed product is transported to the buffer stocker. Therefore, it is possible to minimize the detour transportation, so that efficiency in transportation is enhanced.
According to the present invention, a pod can be kept awaiting in a stocker of a previous process step as long as possible without having process equipment of the next process step waiting for a pod. Therefore, it becomes possible to collect pods at the stocker of the previous step, so that efficiency in transportation is enhanced by transporting thus collected pods at once.
In addition, according to the present invention, a pod awaiting transportation to the next process step does not reside, for example, on an OHS vehicle or in the previous process step. Consequently, the OHS vehicle can be efficiently used to improve the transportation efficiency, and in addition, carry-in/carry-out operations are not hindered at the previous process step.
Furthermore, according to the present invention, a stocker in the next process step is not caused to be full with pods awaiting re-operation of process equipment. Consequently, another pod that uses the same stocker is not hindered from being fed into process equipment. Moreover, since at least one pod is secured in a stocker in the next process step, the pod can be quickly fed, and processing can be quickly started after the process equipment has started operation. Furthermore, the transportation efficiency can be improved by not using a redundant transportation route via the buffer stocker.
Still furthermore, an optimum transportation route can be selected from a route of direct transportation from a stocker in a previous process step to a stocker in the next process step and a route of detour transportation via the buffer stocker.
These and other objects, advantages and features of the present invention will become more apparent from the following description and the accompanying drawings.